Radiation therapy is an important tool in the fight against cancer and is used in the treatment of as many as 50% of all cancer patients. Accordingly, more than half a million cancer patients receive radiation therapy each year. While the use of radiation therapy is an effective way to treat many kinds of cancer, there are many complications that may result. Common complications can include negative effects on the patients skin, hair follicles, and mucous membranes.
Common skin complications of radiotherapy include erythema and folliculitis. These disorders can be very irritating to patients as they both involve pruritus and redness of the skin. These and other skin complications can arise through oxidative and other stress caused by radiation. Other examples of skin conditions caused by radiation include fibrosis, dry desquamation and moist desquamation.
In addition, hair follicles are quite sensitive to radiotherapy. Accordingly, if hair is in the radiation treatment beam field, it can cease to grow and fall out. Losing one's hair can be a source of embarrassment and loss of self esteem.
Radiotherapy can also have negative effects on the mucous membranes in the eyes, nose, mouth, vagina, rectal mucosa and the like. For example, oral mucositis, also called stomatitis, results from the local effects of radiation to the oral mucosa. Mucositis is characterized by inflammation of the mucosa of the mouth and ranges from redness to severe ulceration. Symptoms of mucositis vary from pain and discomfort, to an inability to tolerate food or fluids. Even worse, oral mucositis may be so severe as to limit the patient's ability to tolerate further radiotherapy or chemotherapy.
Patients with damaged oral mucosa and a reduced immunity resulting from radiotherapy are also prone to opportunistic infections in the mouth. Accordingly, mucositis may also further compromise a patient's response to treatment and/or palliative care. It is therefore extremely important that mucositis be prevented whenever possible, or at least treated to reduce its severity and possible complications.
Another common mucous membrane condition caused by radiotherapy is proctitis. Proctitis is an inflammation of the lining of the rectum (rectal mucosa). The most common symptom is a frequent, or continuous sensation, or urge to have a bowel movement. Other symptoms include constipation, a feeling of rectal fullness, left-sided abdominal pain, passage of mucus through the rectum, rectal bleeding, and anorectal pain.
Some have previously suggested the use of Tempol, a stable nitroxide radical characterized by the chemical formula 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl, as a topical formulation to ameliorate the effects of radiotherapy. (See e.g., Proctor, U.S. Pat. No. 5,352,442, and Mitchell, U.S. Pat. No. 5,462,946, both of which are hereby incorporated by reference in their entireties). These references limit the topical use of Tempol to formulations selected from creams, lotions, shampoos, cream rinses, and ointments. It is now recognized that these kinds of topical formulations are unsuitable for administration shortly before the actual delivery of radiotherapy to the patient. Indeed, these product forms leave residues that can result in topical burning, including severe burns, when radiation is administered. Accordingly, there is a need in the art to provide a topical formulation that can be administered to a patient shortly before the actual delivery of radiotherapy.